UNIVERSITY    OF    CALIFORNIA 

COLLEGE   OF   AGRICULTURE 

AGRICULTURAL    EXPERIMENT   STATION 

BERKELEY,  CALIFORNIA 

CIRCULAR  No.  282 
February,  1925 

PREVENTION  OF   INSECT  ATTACK 
ON  STORED  GRAIN 

By  W.  W.  MACKIE 


INTRODUCTION 

Seed  ^rain  is  stored  for  a  number  of  reasons  bj^  farmers  and  by 
cereal  experimenters.  Farmers  commonly  hold  seed  for  a  second  year 
if  it  is  clean  and  of  high  grade.  Storing  seed  for  more  than  one 
year  kills  certain  fungi — for  instance,  ergot  in  rye  and  wheat.  It  is 
always  advisable  for  farmers  to  hold  a  reserve  of  the  seed  of  excep- 
tional or  rare  varieties  which  might  otherwise  be  lost  because  of 
drought,  hail,  rain,  insect  pests,  and  destructive  fungous  diseases. 

The  experimenter  always  finds  it  necessary  to  store  seed  for  one  or 
more  years  in  order  to  maintain  his  stocks.  All  of  this  stored  seed  is 
subject  to  insect  attack  and  most  investigators  have,  at  times,  suffered 
irreparable  losses  in  this  way. 

The  common  method  of  combating  insects  in  stored  grain  is  by 
destroying  them  after  they  have  begun^  to  attack  the  grain  and  usually 
after  considerable  damage  has  been  done.  The  three  most  reliable 
and  commonly  used  insecticide  agencies  are  (1)  carbon  bisulphide 
gas,  (2)  cyanide  gas,  and  (3)  heat.  Each  is  very  effective  when 
properly  used  with  suitable  equipment,  but  suitable  equipment  is  often 
unprocurable  economically  on  farms  and  even  in  laboratories.^'  ^'  ^ 
Further  disadvantages  are  the  danger  of  explosions  with  carbon  bisul- 
phide gas,  asphyxiation  by  cyanide  gas,  and  destruction  or  damage 
to  seed  germs  if  subjected  too  long  to  high  temperatures.®  In  no  case 
do  these  remedies  prevent  a  recurrence  of  insect  attacks.  At  intervals, 
more  or  less  frequent,  according  to  climatic  conditions,  a  repetition 
of  treatment  is  necessary.  The  cost  of  the  chemicals  and  of  the 
preparation  of  gas-tight  containers  or  the  special  testing  devices,  is 
considerable.  To  this  must  be  added  the  cost  of  labor.  A  remedy 
which  would  prevent  all  insect  attack  without  the  necessity  of  repeat- 
ing the  process  and  at  a  reasonable  cost,  would  meet  an  urgent  need. 
Such  remedy,  under  conditions  to  be  described,  apparently  has  been 
found  by  accident  in  the  treatment  of  wheat  with  copper  carbonate 
dust  as  applied  to  prevent  bunt  or  stinking  smut. 


UNIVERSITY    OF   CALIFORNIA EXPERIMENT   STATION 


COPPER  CARBONATE  DUST  AS  A  FUNGICIDE 

Before  the  experiments  with  copper  carbonate  as  an  insecticide  are 
presented,  it  may  be  well,  at  this  point,  to  describe  briefly  the  use  of 
this  fungicide  in  controlling  bunt.  Within  a  very  few  years  copper 
carbonate  dust  as  a  bunt  preventive  has  come  into  general  use  on  the 
Pacific  Coast  and  in  many  other  parts  of  the  world  where  bunt  is  a 
serious  limiting  factor  in  wheat  production.  The  virtues  of  copper 
carbonate  dust  as  a  bunt  preventive  may  be  enumerated  as  follows: 

(1)  It  equals  the  liquid  fungicides  bluestone  and  formaldehyde  in 
destroying  bunt  spores,  provided  the  seed  is  not  visibly  darkened  with 
the  spores. 

(2)  It  does  not  injure  the  seed — a  contrast  with  the  severe  damage 
frequently  caused  by  the  two  standard  liquid  fungicides. 

(3)  Early  and  vigorous  germination  of  the  seed  is  fostered. 

(4)  Seedling  attacks  by  soil  fungi,  like  Penicillium  and  Asper- 
gillus, are  prevented  and  bunt  infection  from  soil-borne  spores  is 
greatly  reduced. 

(5)  Better  percentages  of  germination  and  better  stands  are 
secured  than  with  seed  treated  by  the  liquid  fungicides. 

In  an  earlier  paper,^^  it  was  pointed  out  that  the  use  of  this 
fungicide  results  almost  invariably  in  larger  crops  than  those  obtained 
when  the  seed  is  treated  with  the  common  liquid  fungicides.  Many 
farmers  in  several  widely  separated  states  therefore  consider  that 
copper  carbonate  dust  applied  to  seed  is  very  profitable  even  where 
no  bunt  is  anticipated.  The  following  experiments  completed  this 
season  at  the  University  Farm,  Davis,  California,  will  serve  to  illus- 
trate the  effects  due  to  the  copper-carbonate  method  of  seed  treatment. 

Three  plots  were  drilled  with  bunted  Hard  Federation  wheat 
treated  as  follows : 

TABLE  1 

Effect  of  Copper  Carbonate  on  Bunt  and  Yield  of  Wheat 

AT  Davis,  California 


Seed  treatment 

Bunt, 
per  cent 

Heads,  90  feet 
of  drill  row 

Heads,  per  cent 
compared  with 
no  treatment 

Bluestone — lime 

.44 

6.65 

.20 

210 
316 
413 

66.4 

Check — no  treatment 

100.0 

Copper  carbonate,  2  oz.  per  bushel 

131.0 

These  results  show  an  increase  of  yield,  due  to  copper  carbonate, 
of  31  per  cent  over  no  treatment  and  65  per  cent  over  the  bluestone- 
lime  treatment. 


Circular  282]   prevention  of  insect  attack  on  stored  grain  3 

As  there  are  now  a  number  of  effective  dusting  machines  for 
automatically  treating  seed  as  it  comes  from  the  cleaner  and  grader, 
the  labor  cost,  a  large  item  in  the  application  of  the  liquid  fungicides, 
is  greatly  reduced.  Furthermore,  a  great  advantage  is  secured  by 
treatment  of  the  seed  in  the  slack  season  following  the  harvest,  thus 
avoiding  a  loss  of  more  valuable  time  at  the  important  seeding  period. 
This  procedure  is  possible  with  copper-carbonate-dusted  seed  because 
of  two  effects  of  the  chemical  dust.  First,  copper  carbonate  does  not 
in  any  way  injure  stored  grain  regardless  of  the  length  of  time  stored ; 
stored ;  and,  second,  insect  attacks  are  prevented.  The  latter  condition 
will  be  shown  in  the  experiments  which  follow. 

EXPEBMIMENTS  WITH  COPPER  CARBONATE   DUST  AS  AN 

INSECTICIDE 

ObserYations  at  Davis  of  w^heat  seed  treated  with  copper  carbonate 
dust,  stored  from  a  few  months  to  two  years,  showed  that  no  insect 
attacks  occurred  on  dusted  seed,  while  untreated  seed  in  the  same  pile 
was  literally  reduced  to  bran  by  the  attacks  of  the  grain  weevils,  the 
Confused  flour  beetle,  and  the  Angoumois  moth.  Experiments  in 
duplicate  and  at  consecutive  periods  were  conducted  to  determine  the 
effect  of  the  copper  carbonate  dust  in  preventing  insect  attack.  A 
soft  w^hite  wheat  (Pacific  Bluestem)  was  employed  in  these  experi- 
ments because  hard  wheats  are  not  so  readily  attacked  by  insects.  The 
insects  and  seed  were  confined  in  stoppered  bottles  and  the  insects 
examined  daily  with  the  following  results: 

TABLE  2 

Effect  of  Copper  Carbonate  on  Grain  Weevils  in  Wheat  Stored  at 

Berkeley,  California 


June  23 

June  24 

June  25 

June  26 

June  27 

June  28 

June  30 

July  1 

July  14 

;3 

1 

■a 

Q 

0) 

> 

Q 

a; 
> 

T3 

Q 

> 

1 

> 

1 

> 

;3 

> 

3 

o 
Q 

;3 

1 

(1)    Grain  weevils: 

Wheat  untreated 

50 

50 
50 

50 
6 

0 

0 
0 

0 
0 

48 

50 
49 

50 
5 

2 

0 
1 

0 

1 

46 

50 

48 

50 
4 

2 

0 

1 

0 

1 

41 

49 
36 

35 
3 

5 

1 
12 

15 

1 

40 

46 
19 

25 
3 

1 

3 

17 

10 
0 

39 

27 

7 

18 
3 

1 

19 
12 

7 
0 

35 

3 

0 

0 
1 

4 

24 

7 

7 
2 

30 

0 
0 

0 

1 

5 

3 
0 

0 
0 

23 

0 
0 

0 
0 

7 

0 
0 

0 

1 

Wheat -l-CuCo3,    2     oz.    per 
bushel 

(2)    Wheat +CuCo3,      2      oz.     per 

(3)    Confused  flour  bettle: 

Wheat +CuCo3,    2     oz.    per 
bushel                       .        

(1)  Grain  weevil  {Sitophilus  [Calandra]  granaria  (Linn.). 

(2)  The  cloth  permitted  about  half  of  the  weevils  to  enter  the  dusted  seed  but  all  died  eventually  on 
account  no  doubt,  of  breathing  the  dust. 

(3)  Confused  flour  beetle  {Tribolium  confusum  Duv.). 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

From  the  very  beginning,  the  weevils  that  came  in  contact  with  the 
copper  carbonate  dust  showed  distress  and  were  very  sluggish  in  their 
movements.  The  beetles,  on  the  contrary,  did  not  slow  up  in  their 
movements.  None  of  the  insects  apparently  fed  or  laid  eggs  in 
the  presence  of  copper  carbonate.  All  of  the  weevils  exposed  to  the 
dust  were  dead  at  the  end  of  six  days,  and  the  beetles,  at  the  end  of 
eight  days.  Even  those  weevils  which  were  prevented  from  coming 
in  contact  with  the  dusted  wheat,  but  were  exposed  to  the  dust  con- 
taminated air  of  the  closed  bottle,  died  as  rapidly  as  those  actually 
coming  in  visible  contact  with  the  dust. 

In  another  experiment,  many  hundreds  of  live  Angoumois  moths 
(Sitotroga  cerealella  Oliv.),  confined  in  a  jar  half -filled  with  a  portion 
of  the  same  treated  wheat,  did  not  lay  eggs  although  they  lived  for  a 
period  of  three  weeks  or  more,  eventually  dying  of  age  without  the 
production  of  larvae. 

THE  NATUKE  OF  CHEMICAL-DUST  INJURY  TO  INSECTS 

Contact  insecticides  commonly  are  understood  to  be  substances 
which,  when  dissolved  or  emulsified  in  liquid  media,  or  contained  in 
dusts,  are  capable  of  killing  insects  when  brought  in  contact  with 
them.^*  In  these  experiments,  we  are  not  concerned  with  those  sub- 
stances contained  in  the  dust  form  which  are  stomach  poisons  and 
which  therefore,  to  become  effective,  must  be  eaten.  Dust  contact 
insecticides  cause  death  to  insects,  first,  by  fumes  given  off,^^  second, 
by  the  entry  of  the  dust  particles  into  the  respiratory  system,  and 
third,  by  corrosive  action  upon  the  softer  portions  of  their  bodies. 
The  most  important  example  of  a  dust  insecticide  of  the  first  class  is 
nicotine.^^'  ^^  R.  E.  Smith^^  states  that  the  walnut  aphis  is  killed 
solely  by  the  fumes  from  the  nicotine  dust.  Mclndoo,^^  however, 
believes  that  particles  of  the  tobacco  dust  pass  into  the  trachea  and 
are  widely  distributed  to  the  tissues  of  the  body,  causing  paralysis 
and  death  of  the  insect.  This  result  appears  to  be  confirmed  by 
CampbelP  in  his  experiments  with  the  melon  and  cabbage  aphids, 
onion  thrips,  and  cucumber  beetles.  Sulphur  and  lime^^  have  been 
used  as  contact  poisons  but  have  given  either  negative  or  poor  results. 
Caustic  lime  may  be  effective  against  certain  soft  insects  until  it 
changes  its  form  into  air-slacked  lime,  or  calcium  carbonate.  As  the 
change  from  caustic  to  air-slacked  lime  is  rapid  the  caustic  effect  is 
limited  to  a  very  short  period.  For  this  reason  the  application  of 
lime  to  stored  grain  has  not  proved  of  much  value  against  hard- 
shelled  insects  as  the  grain  beetles  and  weevils. 


Circular  282]    prevention  OF  INSECT  ATTACK  ON  STORED  GRAIN  5 

THE  ACTION  OF  COPPER  CARBONATE  ON  INSECTS 

The  injurious  effect  of  copper  carbonate  dust  on  weevils  appears 
first  in  their  retarded  movements.  The  insects  become  less  and  less 
active  until  death  ensues.  No  weevil  lives  longer  than  six  days  after 
having  come  in  thorough  contact  with  this  du>st.  The  very  evident 
distress  of  the  insect  in  contact  with  the  dust  apparently  causes  a 
cessation  of  all  feeding  and  reproductive  activities.  The  beetles  are 
naturally  more  9,ctive  in  their  behavior  and  all  die  by  the  end  of  the 
eighth  day  of  confinement  in  contact  with  the  copper  carbonate  dust. 

1^  (ft 


♦i 


Fig.  1. — Grain  Weevil  SitopMlus  (Calandra)  granaria  (Linn.) 

Left,  normal  weevils.    Right,  weevils  covered  with  the  copper  carbonate 

which  killed  them. 

The  action  of  the  copper  carbonate  is  limited  to  its  caustic  effect. 
This  chemical  compound,  consisting  of  varying  proportions  of  copper 
carbonate  and  copper  hydrate  (CuCOs  •  CuCOH)^)  is  listed  by  chemists 
as  insoluble  in  water  but  slowly  soluble  in  certain  dilute  organic  and 
inorganic  acids.^^  As  the  particles  of  copper  carbonate  dust  are  very 
adhesive  even  to  extremely  smooth  surfaces,  the  rough  coated  weevils 
and  beetles  soon  become  completely  covered  while  crawling  about  in 
the  dusted  seed  (fig.  1).  The  softer,  moister  surfaces,  especially  in 
creases  between  the  joints  of  the  legs,  thorax,  and  prothorax,  appear 
to  be  most  affected  by  the  chemical  dust.  No  doubt  a  portion  of  the 
salt  goes  into  solution  through  the  action  of  the  solvents  on  the 
moist,  soft  surfaces  of  the  insects.  This  chemical  reaction  eventually 
causes  death. 


b  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Undoubtedly  minute  particles  of  copper  carbonate  dust  enter  the 
respiratory  system  of  the  insects.  In  one  of  the  experiments  with 
weevils,  the  insects  were  screened  away  from  the  dusted  seed  con- 
tained in  the  bottom  of  the  closed  receptacle.  These  weevils,  which 
did  not  come  into  direct  contact  with  the  copper-carbonate-dusted 
wheat  seed,  nevertheless  died  as  soon  as  those  which  entered  the  mass 
of  treated  seed.  This  is  readily  explained  when  the  amorphus,  very 
finely  divided  condition  of  the  copper  carbonate  dust  is  considered. 
The  dust  is  so  li^ht  and  imp  alp  ably  fine  that  it  remains  suspended 
in  air  over  long  periods  of  time,  and  in  a  confined  space  is  not  carried 
away.^  Likewise,  when  copper  carbonate  dust  is  placed  where  wing- 
less, crawling  insects,  like  the  grain  weevil,  must  come  in  contact 
with  it  in  order  to  reach  the  stored  grain,  the  seed  is  not  attacked 
and,  therefore,  is  fully  protected  against  this  class  of  insects. 

INSECTS  WHICH  SHOULD  EEACT  TO  COPPEE  CAEBONATE  DUST 

In  the  experiments  described  in  this  paper,  the  common  grain 
weevils  and  beetles  were  effectively  destroyed  without  injury  to  the 
wheat  seed.^'  ^  Other  insects  in  the  weevil  and  beetle  group  likely 
to  succumb  to  copper  carbonate  dust  may  include  the  rice  weevil 
8itophiliis  oryzae  (L.),  the  saw-toothed  grain  weevil  Oryzaephihis 
surinamensis  (L.),  the  foreign  grain  beetle  Cathartus  advena  (Walt.), 
the  square-necked  grain  beetle  Laemophloeus  pusillus  (Schon.),  the 
rust-red  flour  beetle  Tribolium  ferrugineum  (Fab.),  and  the  small- 
eyed  flour  beetle  Palorits  ratzehurgi  (Wissm.). 

The  benefits  to  be  derived  by  the  prevention  of  insect  invasion  of 
stored  seed  in  the  southern  states  or  in  warm  regions^ ^  by  this  simple 
and  cheap  remedy  suggests  trials  in  these  areas. 

In  conclusion,  it  appears  from  the  results  of  these  experiments 
that  a  new,  cheap,  very  effective,  easily  applied  remedy  for  the  pre- 
vention and  control  of  weevil  and  beetle  attacks  upon  stored  grain 
has  been  secured. 

HOW  TO  APPLY  THE  COPPEE  CAEBONATE  DUST 

Copper  carbonate  dust  is  applied  to  wheat  at  the  rate  of  two 
ounces  per  bushel.  Double  this  quantity  is  sometimes  applied  but  is 
usually  unnecessary  and,  besides,  the  fine  dust  is  offensive  to  humans 
and  to  work  animals.  Large  machines^^  are  available  for  treating 
large  quantities  of  seed  grain  in  connection  with  warehouses.^" 
Portable  machines  driven  by  hand  or  by  motor  power  are  manuf ac- 


Circular  282]    prevention  op  INSECT  ATTACK  ON  STORED  GRAIN  7 

tured  on  the  Pacific  Coast.  This  latter  class  of  dusters  is  adapted  to 
farms  of  ordinary  size  or  to  groups  of  farms.  For  small  lots  of  seed, 
a  box  turned  upon  an  axle  passing  through  the  corners  diagonally  is 
quite  satisfactory.® 

Copper  carbonate  may  be  also  used  to  afford  some  protection  to 
stored  grain  of  any  kind  by  placing  it  where  crawling  insects  must 
pass  it  to  get  into  the  grain.  It  should  not  be  placed  on  grain  to  be 
used  for  animal  or  human  food. 


LITERATURE  CITED 

1  Campbell,  Ray  E. 

1921.     Nicotine  Sulphate  in  a  Dust  Carrier  against  Truck  Crop  Insects. 
U.  S.  D.  A.  Cir.  154:3-13. 

2  Carleton,  M.  a. 

1917.     The  Small  Grains,  pp.  471-504. 

3  Chittendon,  F.  H. 

1910.  Control  of  the  Mediterranean  Flour  Moth  by  Hydrocyanic  Acid  Gas 

Fumigation.     U.  S.  D.  A.  Bur.  Ent.  Cir.  112:1-13. 

4  Chittendon,  F.  H. 

1911.  A  List  of  Insects  Effecting  Stored  Products.     U.  S.  D.  A.  Bur.  Ent. 

Bull.  96:36-46. 

5  Cory,  E.  N. 

1920.     Report  of  Dusting  and  Spraying  Investigations.     Maryland  Agron. 
Soc.  Rep.  5:318-327. 

6  Dean,  G.  A. 

1913.  Mill  and  Stored  Grain  Insects.     Kansas  Agr.  Exp.  Sta.  Bull.  189: 

198-235. 

7  Hinds,  W.  A. 

1914.  Reducing  Insect  Injury  to  Stored  Corn.     Alabama  Agr.  Exp.  Sta. 

Bull.  176:52-57. 

8  Hoffman,  A.  H. 

1924.     A  Miniature  Copper  Carbonate  Duster.     Jour.  Amer.  Soc.   Agron. 
16:481-482. 

9  Mackie,  W.  W. 

1919.     Quarantines    against    ''Flag    Smut"    and    ''Take-all."      Monthly 
Bulletin  of  the  Dept.  of  Agri.  State  of  California  8:456^60. 

10  Mackie,  W.  W.,  and  Briggs,  Fred  N. 

1923.     Fungicidal  Dusts  for  the  Control  of  Bunt.     California  Agr.  Exp. 
Sta.  Bull.  364:554-563. 

11  MacLeod,  G.  F.,  and  Harm  an,  S.  W. 

1923.     The  Aphididal  Properties  of  Tobacco  Dust.    New  York  State  Bull. 
502:3-18. 


8  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

12  MclNDOO,  N.  E. 

1916.     Effects  of  Nicotine  as  an  Insecticide.    Jour.  Agr.  Besearch  3:82-106. 

13  Piper,  C.  V. 

1924.     Forage  Plants  and  Their  Culture,  pp.  512-513. 

14  Richardson,  Charles  H.,  and  Smith,  C.  R. 

1923.  Studies  on  Contact  Insecticides.     U.  S.  D.  A.  Bull.  1160:10-13. 

15  Smith,  J.  B. 

1903.     Insecticides  and  Their  Use.     New  Jersey  Agr.  Exp.  Sta.  Bull  169: 
21-25. 

16  Smith,  R.  E. 

1921.     The  Preparation  of  Nicotine  Dusts  as  an  Insecticide.     California 
Agr.  Exp.  Sta.  Bull.  336:267-271. 

17  Snaps,  O.  I. 

1924.  Dusting  and  Spraying  of  Peach  Trees  after  Harvest  for  Control  of 

Plum  Curculio.     U.  S.  D.  A.  Bull.  1205:5-10. 

18  Thatcher,  R.  W.,  and  Streeter,  Jj.  R. 

1923.     Factors  which  Effect  the  Volatility  of  Nicotine  from  Insecticide 
Dusts.     New  York  State  Exp.  Sta.  Bull.  501:3-5. 


15m-3,'25 


